Parkinson's disease is a neurodegenerative disorder characterized by a chronic and progressive loss of dopamine neurons in substantia nigra pars compacta, leading to movement disorders including dyskinesia, resting tremor, rigidity, and gait disturbance.
The medical treatment of Parkinson's disease is directed to stopping, slowing down, reducing the extent of or minimizing the neurodegenerative process in nigrostriatal neurons (neuroprotective therapy) and eliminating the biochemical imbalance (symptomatic therapy). The main directions of symptomatic therapy in Parkinson's disease are to increase dopamine synthesis, or stimulate dopamine receptors activity and dopamine release from the presynaptic space, and to inhibit dopamine reuptake by presynaptic receptors and dopamine catabolism.
The gold standard in the pharmacological treatment of Parkinson's disease is provided by DOPA-containing substances such as levodopa. Levodopa is commonly administered in combination with carbidopa, which increases the half-life of levodopa. However, the efficacy of these agents decreases over time because of continuing degeneration of neurons in the substantia nigra.